Motor vehicles include an airbag system consisting of impact sensors, a system controller, an inflator, and the inflatable airbag cushions themselves. The inflatable airbag cushions are stored for deployment at a number of locations inside a motor vehicle and, when deployed into the passenger cabin in the event of a collision, protect the vehicle occupants from injury. For example, inflatable airbag cushions are stored at concealed locations behind deployment doors within the steering wheel for protection of the driver and in the instrument panel for protection of a passenger during a collision event. Airbag systems may also be provided in other trim assemblies throughout the vehicle.
Concealing each airbag cushion is a deployment door that forms an interior portion of the vehicle, such as a portion of the steering wheel hub, instrument panel or other trim assembly. Typically, the deployment door covers an opening through which the airbag cushion is deployed in the event of a collision. When the airbag cushion inflates, the deployment door is opened by the force applied by the inflating airbag cushion against the deployment door.
Designers of interior trim assemblies, however, have been challenged with providing effective deployment of an airbag cushion while providing a pleasing aesthetic appearance of the interior trim assembly through which the airbag cushion deploys. Designers of interior trim assemblies have also been challenged to provide such interior trim assemblies in a cost effective manner. In several designs, a trim assembly has a multi-portion construction, including a retainer portion, which comprises a significant part of the trim assembly, and a deployment door that overlies the airbag cushion located immediately behind the trim assembly. In many of these designs, the trim assembly has a visible seam having a low resistance to normal and shear stresses to allow the airbag cushion to deploy therethrough. This seam clearly distinguishes the deployment door from the retainer portion of the trim assembly and consequently detracts from the aesthetic appearance of the automotive interior.
Another consideration for designers of trim assemblies deals with preventing the deployment door from being ejected into the passenger compartment at a high rate of speed during the deployment of the airbag cushion. Many designs include a hinge mechanism located on the interior or back side of the deployment door adjacent the airbag cushion with one end coupled to the back side of the deployment door and another end coupled to a fixed support. The hinge mechanism is typically placed on the back side of the deployment door so that it is not visible from the passenger compartment and does not detract from the aesthetic appearance of the automotive interior.
For instance, several designs use a tether made of natural fibers, synthetic fibers, thermoplastic materials or other suitable materials, having one end coupled to the deployment door through adhesives, vibration or sonic welding techniques, or other methods. The opposed end of the tether is then attached to the airbag housing or other automotive support. In this way, the tether functions as a hinge that allows, or otherwise facilitates, pivotal movement of the deployment door so as to prevent the door from separating from the trim assembly when the airbag cushion is deployed.
Hinge mechanisms located on the interior side of the deployment door have some drawbacks. In particular, so as to accommodate the pivotal movement of the deployment door, the hinge mechanism may have a loosened or slack region when the airbag cushion is in the stored or non-deployed state. Consequently, the hinge mechanism is susceptible to hinge binding, which may lead to the improper functioning of the airbag system when actuated. Additionally, incorporating a separate hinge mechanism into the airbag system requires additional parts and labor which increase the overall cost of the trim assembly.
There is a need for an improved interior trim assembly having an airbag deployment door that enhances the aesthetic appearance of the automotive interior, increases airbag reliability and reduces the number of parts, labor and overall manufacturing costs.